import UIKit

class CalendarViewController: UIViewController {


    @IBOutlet weak var calendarCollectionView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
        let layout = CalendarLayout()
        calendarCollectionView.collectionViewLayout = layout

//        calendarCollectionView.register(HeaderView.classForCoder(), forCellWithReuseIdentifier: "HeaderView")

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

class CalendarLayout: UICollectionViewLayout {
    override var collectionViewContentSize: CGSize {
        return super.collectionViewContentSize
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        return super.layoutAttributesForElements(in: rect)
    }

    override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        return super.layoutAttributesForItem(at: indexPath)
    }

    override func layoutAttributesForSupplementaryView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        return super.layoutAttributesForSupplementaryView(ofKind: elementKind, at: indexPath)
    }

    override func layoutAttributesForDecorationView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        return super.layoutAttributesForDecorationView(ofKind: elementKind, at: indexPath)
    }

    override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return true
    }
}


extension CalendarViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 5
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CalendarEventCell", for: indexPath) as? CalendarEventCell ?? CalendarEventCell()

        cell.titleLabel.text = "Title \(indexPath.row)"

        return cell
    }

    func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "HeaderView", for: indexPath) as? HeaderView ?? HeaderView()

        headerView.titleLabel.text = "header title"

        return headerView
    }
}